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Jacksonville Mosquito Forecast

Today's mosquito activity in Jacksonville, the week ahead, and what to do about it. Updated hourly.

Bite Index · Sunday, November 8

Severe

Severe mosquito activity in Jacksonville today and easing through the week. Expect to be bitten within minutes outdoors at dusk.

Swarming conditions. Expect bites within a minute or two outside at dusk.

Worse than a typical November in Duval County (usually around 56).

  • 1.3 in. of rain Oct 23–Oct 31 is now producing adults (cool weather slowed the hatch, so the window is longer than usual).
  • Tonight: a 67°F evening, light wind — good flying weather for mosquitoes.
  • A two-week average of 72°F keeps populations growing, just more slowly than midsummer.

The week ahead

Each day's Bite Index, from this week's weather and the rain that is still hatching. Forecast days get less certain as the week goes on.

  1. Today
    86Severe79°/56°dry
  2. Mon
    89Severe78°/59°dry
  3. Tue
    89Severe84°/57°dry
  4. Wed
    86Severe80°/69°dry
  5. Thu
    88Severe79°/66°dry
  6. Fri
    68V·High69°/49°dry
  7. Sat
    66V·High60°/42°dry

Protect tonight

Treat the outdoors like a swarm: cover up and use a full-strength repellent.

  1. 25–30% DEET or 20% picaridin on every bit of exposed skin, plus permethrin-treated clothing for anything longer than a quick trip outside.
  2. Keep kids and pets in around dusk and dawn; schedule outdoor time for midday when it's hottest and driest.
  3. If your health department has an active West Nile advisory for your ZIP, follow it over anything on this page.
Which repellent, and how much: DEET vs picaridinBest natural repellents

Why Jacksonville's mosquitoes do what they do

Jacksonville is the largest city by area in the lower 48, wrapped around the St. Johns River and the salt marshes of the Intracoastal, with a climate that is tropical in summer and cool enough in winter to actually pause the season. The city's Mosquito Control Division posts where it is spraying and will inspect yards on request.

  • Salt marsh: the Intracoastal and the Timucuan marshes produce big salt-marsh Aedes broods after spring tides and tropical rain.
  • St. Johns River and its creeks: slow blackwater habitat through the heart of the city.
  • Summer storms: June through September rain on sandy soil drains fast in uplands but stands in the many low, wooded lots.
  • A real winter lull: Duval County drops to low or asleep in December and January most years.

A typical year in Duval County

The long-run mosquito index by month from our season map (NOAA climate normals plus effort-corrected sightings). Today's Bite Index is the live version of this; the month you're in is marked.

  1. JJanuary: 21
  2. FFebruary: 24
  3. MMarch: 36
  4. AApril: 52
  5. MMay: 70
  6. JJune: 87
  7. JJuly: 94
  8. AAugust: 97
  9. SSeptember: 100
  10. OOctober: 84
  11. NNovember: 56
  12. DDecember: 30

Local surveillance and West Nile virus

The Bite Index measures nuisance biting, not disease. Duval County's health department traps and tests mosquitoes through the season and publishes positive West Nile pools by ZIP code. When your ZIP has an active advisory, follow it regardless of today's number.

How the Bite Index is scored

The index is a model of conditions, not a mosquito count. Four weather factors are combined on a 0–100 scale, then scaled by the season. Every factor and today's value for it is listed here so you can check the number yourself. It uses the same temperature curve and rain logic as our county-level mosquito season map, which has been validated against effort-corrected sighting data across 41 states.

BBreeding pressure

Rain 7–14 days ago (1.4 in. between Oct 23 and Oct 31). Eggs need water to hatch, and at summer temperatures the egg-to-biting-adult cycle takes about a week, so today's mosquitoes are last week's rain. Cool weather stretches the window; hot dry days shrink it as shallow water evaporates.

Weight 40%
Today 88%

DDevelopment

The trailing two-week average temperature, on the same curve as our national season map: nothing below 50°F, full speed at 78–88°F, a small penalty in extreme heat.

Weight 25%
Today 78%

ATonight's activity

Whether the population that exists will actually fly and bite this evening: dusk temperature (65–85°F is ideal), wind (they stop flying around 10 mph), humidity, and rain around sunset.

Weight 25%
Today 100%

GGround truth

A nudge from local trap counts and reports when we have them. For Jacksonville this is neutral today; the health department's surveillance is linked above and will feed this factor as we wire it in.

Weight 10%
Today neutral

SSeason gate

A multiplier from the calendar: fully open in the city's season months, half-open in the shoulder months, nearly closed in deep winter unless the week is warm. Below a 50°F weekly average the index is simply 0.

Weight ×
Today 100%

index = 100 × S × (0.40 × (0.2 + 0.8·B) + 0.25 × D + 0.25 × A + 0.10 × (0.5 + 0.5·G))

Bands: Low 0–20 · Moderate 21–40 · High 41–60 · Very High 61–80 · Severe 81–100. Weather is from Open-Meteo (observations and the 7-day forecast), refreshed hourly. The lag and temperature thresholds follow published work on Culex and Aedes development (Rueda et al. 1990; Cornell NRCC degree-day emergence; JAMCA 2024 on rainfall two to four weeks before trap peaks).

Questions people ask about mosquitoes in Jacksonville

When is mosquito season in Jacksonville?
March through November, peaking from June through October. Unlike South Florida, Jacksonville gets a genuine winter lull when nights fall below about 50°F.
Why are mosquitoes worse near the beaches?
Salt-marsh mosquitoes hatch in huge numbers when spring tides or heavy rain flood the marsh, and they fly miles inland. The beach communities and anything along the Intracoastal get them first.
Is West Nile virus a risk in Jacksonville?
Yes. Duval County has recorded West Nile and EEE activity in most years, and the health department issues advisories. Follow those over the Bite Index.
Where does this forecast's data come from?
Open-Meteo weather for central Jacksonville, scored by our documented model. It does not include tide data, which drives salt-marsh broods, so treat a big tide as an extra reason for caution.

Also covers Jacksonville Beach, Orange Park, St. Augustine, Fernandina Beach, Ponte Vedra, Mandarin, Riverside, Hanna Park: the forecast point is central Jacksonville, and conditions within about 30 miles track it closely. Weather fetched Nov 8, 1:38 PM local time.

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